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Plasma catecholamine and blood lactate responses to incremental arm and leg exercise

2000; Lippincott Williams & Wilkins; Volume: 32; Issue: 3 Linguagem: Inglês

10.1097/00005768-200003000-00009

1530-0315

Donald A. Schneider, Tom M. McLellan, Greg C. Gass,

Muscle activation and electromyography studies

SCHNEIDER, D. A., T. M. McLELLAN, and G. C. GASS. Plasma catecholamine and blood lactate responses to incremental arm and leg exercise. Med. Sci. Sports Exerc., Vol. 32, No. 3, pp. 608–613, 2000. Purpose and Methods: The present study was conducted to examine the pattern of plasma catecholamine and blood lactate responses to incremental arm and leg exercise. Seven untrained male subjects performed two incremental exercise tests on separate days in random order. One test consisted of 1-arm cranking (5W·2 min−1), whereas the other exercise test was 2-leg cycling (20–25W·2 min−1). Blood samples were obtained from the nonexercising arm during 1-arm cranking and from the same arm and vein during 2-leg cycling. Thresholds for blood lactate (TLa), epinephrine (TEpi) and norepinephrine (TNE) were determined for each subject under both exercise conditions and defined as breakpoints when plotted as a function of power output. Results: When the two modes of exercise were compared, TLa, TEpi, and TNE were all significantly lower for 1-arm cranking than for 2-leg cycling (P < 0.01). During 1-arm cranking, TLa (0.96 ± 0.10 L·min−1), TEpi (1.02 ± 0.07 L·min−1), and TNE (1.07 ± 0.09 L·min−1) occurred simultaneously. During 2-leg cycling, TLa (1.77 ± 0.20 L·min−1), TEpi (1.74 ± 0.17 L·min−1), and TNE (1.98 ± 0.17 L·min−1) occurred at similar levels of V̇O2 and were not significantly different. The correlation observed between the V̇O2 measured at the TLa and TEpi was 0.917 for arm and 0.929 for leg exercise (P < 0.001). The epinephrine concentration ([Epi]) obtained at the TLa was not significantly different for arm (0.144 ng·mL−1) and leg (0.152 ng·mL−1) exercise. Conclusions: The breakpoint in plasma [Epi] shifted in an identical manner and occurred simultaneously with that of TLa regardless of the mode of exercise (arm or leg). The Epi concentrations observed at the TLa agree with those previously reported to produce a rise in blood lactate during Epi infusion at rest. These results support the hypothesis that a rise in plasma [Epi] may contribute to the breakpoint in blood lactate that occurs during incremental exercise.